driveshaft angle

[Doc Dave]

I have started the tear down of my 1953 m37 project, the "bulldog".
I have the cab, bed and engine off of the frame.
I have a centered rear from a WC truck to use on it, with the axles. I noticed that the driveshaft angle from the NP 200 TC back to the stock diff is relatively steep. I noted that the ebrake output (center) shaft on the TC is an inch or two higher than the stock side shaft going back.
Is the additional angle that will result a potential problem here?

[Frank Irons]

Yes there are some potential problems. You may have to shim your rear axle, transfer case, or both to get a good operating angle. You could also use a double Cardan joint on one end of your driveshaft and re align the spring perches on the axle housing. The track width of the WC axle housing is also 2.5 inches wider than the M37.

Frank

[Doc Dave]

Thanks Frank,
SInce I have to reattach spring perches a little inboard on the centered axle to match the M37 spring pack, I wonder if focusing on the perches would be the easiest way to handle this issue.
I am thinking I will first measure the stock driveshaft angle.
Then attach the perches at the correct spring pack width at a slightly different angle so as to turn the differential up slightly to make the angle the same as before.
Does this sound logical?
Of course I could ship the TC a bit to point the rear down, but then I wonder about the front, although I think it is fairly level with the NP420. I did not measure it before I pulled the engine/tranny but could if needed.

[Gordon Maney]

If you look at the two shafts connected by a driveshaft -- in your case, the transfer case rear output and the rear axle's pinion shaft -- they should be parallel. Imagine that layout, that relationship.

If you address issues to the rear, you have the possibility of creating them to the front. Consider that the truck will most often run in two wheel drive, utilizing that rear driveshaft setup. It needs to be right since it is going all the time.

The front only runs when you engage front drive. I have seen some folks build front driveshafts with constant velocity universal joints to deal with this issue.

[W_A_Watson_II]

With a typical driveshaft, your pinion angle should be close to parallel to your T-case output shaft.With a CV driveshaft, the normal load condition should be a zero degree angle, and the CV Joint should take up the alignment.

The above shows some good info for transnational NON-CV drive shafts.

Will

[Frank Irons]

Thanks Frank,
SInce I have to reattach spring perches a little inboard on the centered axle to match the M37 spring pack, I wonder if focusing on the perches would be the easiest way to handle this issue.
I am thinking I will first measure the stock driveshaft angle.
Then attach the perches at the correct spring pack width at a slightly different angle so as to turn the differential up slightly to make the angle the same as before.
Does this sound logical?
Of course I could ship the TC a bit to point the rear down, but then I wonder about the front, although I think it is fairly level with the NP420. I did not measure it before I pulled the engine/tranny but could if needed.

Assemble with what you have and see what geometry you are dealing with. You may be able to deal with excessive angles with shimming and stock components. Will's post is an excellent example of options if you need them. If you go to the double cardan the rear axle pinion is generally pointed straight to the transfer case and the double joint takes up all the irregularities, however the joint and connection to the transfer case are more complex, and expensive.

Frank

[Doc Dave]

Thanks Will, Gordon and Frank for your excellent advice.
I will post what I discover as to the angles when I get to that stage.

[Matthew Ziegler]

driveshaft angles

I helped a friend of mine do a spring over axle conversion on a 93 jeep and we ran into some similar issues. The way we dealt with it was basically put the whole thing together without welding the spring perches to the axle tubes. This saves a lot of speculation and measuring, nothing like a good visual. Once it looked good he tacked the perches to the axle tubes, removed the rear from under the truck and welded them in place. when you weld them on do about an inch on each side and let it cool then go back and do it again,I'm told too much heat can cause the axle tube to bend or distort. I like the cv driveshaft idea, there's a driveshaft shop here in jersey who makes up custom driveshafts, lots of race and fourwheel drive stuff, look up Axle Exchange in Fairfield NJ if your interested.

[Doc Dave]

Thanks Matthew, good advice.